Process and apparatus for dehydrating oils



July 26, 1932 L. 1 DAVIS 1,869,008

PROCESS AND APPARATUS FOR DEHYDRATING OILS Filed Feb. ll. 1929 IN VENTOR Q01/.0 L HAI/JJ y (tm EY Patented July 26, 1932 curr STATES PATENTOFFECE LLOYD L. DAVIS, OF PONGA CTY, OKLAHOMA, ASSIGNOR TO CONTINENTALOIL COM- PANY, OF EONCA CITY, OKLAHOMA, A CORPORATION OF DELAWAREPROCESS AND yAPPARATUS FOR `l'JIEIEIYDRATCNGr OILS Application ledFebruary 11, 1929. Serial No. 339,034.

This invention relates to the dehydration of refined and unrefinedpetroleum lubricants in such a manner that the water may be completelyremoved from the rened lubricants for loading into tank cars forshipment and that the unrefined petroleum lubricants may be freed ofwater which improves the stock for further processing.

n The primary object of this invention is to provide a process andapparatus for the complete removal of water from refined lubricantsprior to shipment. The usual method of dehydrating lubricants prior toshipment nis to blow the oil with air until all of the i5,j moisture isremoved. The air causes the oil V,to lose color and to become unstable,whereas the use of my process and apparatus for` dehydrating oilscompletely eliminates l the loss and any increase in unstability of the'2d product otherwise brought about by the old methods. The air blowingmethod of dehydrating involves both chemical and physical action. `Mymethod eliminates the chemical action which is injurious to the oilandeffects dehydration of the oil without injurious effects to the oiland withoutobjectionable changes in color. Another object is tocompletely dehydrate unrefined petroleum lubricants and bring about animprovement in the condition of such products which will enable reiiningprocessing, as acid treatment, Contact and percolating filtration, etc.,to be carried out more effectively and economical- `ly. Still anotherobject of the invention is to provide a process and apparatus in whichthe `separation of water is continuously and completely edected, thusobviating the use of tanks required in the old and well-known method ofdrying the oil by air blowing.

The principles involved in this proc-ess and apparatus `are heat, vacuumand distribution of the oil in thin films so that the forces opposingthe evaporation of the water are 'lessened. The waterin the oil isthought to be usually in the form of minute droplets,'com pletelysurrounded by a film of oil, although at times it may also be present inthe form of a film surrounding minute droplets of oil. Theeifect ofheat, vacuumand thin film disv tribution is to reduce the surfacetensionof both oil and water droplets; to effect vaporization at comparativelylow temperatures of such water as may be present; the temperature of themass being raised to a point higher than the boiling temperature of themoisture at the vacuum carried is thought to reduce the surface tensionof the bubble film and cause the bubble to increase in size until theexpanding water vapor breaks the film and escapes. The action is notinstantaneous, a more or less definite time being required for it totake pla-ce. Sulflciently high temperatures must be used to bring abouta` fairly quicker rupture of the films and consequent release of thewater and water vapor present, as too slow a release of the water andwater vapor will .result in a foaming action of the combined Water vaporand oil. Let it be understood that the process is independent of anyprojected theory, but is the result of tests on oils. lf a droplet ofwater is enclosedl in a body o-f oil, its tendency to vaporize or tochange from liquid to vapor is lessened. If the oil is distributed in athin film on a plate and if the oil has been heated so that theviscosity and surface tension are lowered, the oil will drain away fromthe bubbles and the resistance to evaporation of-v fered by the surfacetension of the oil will be lessened. If the conditions are such that thewater is in the form of vapor, or in other words` a foam, then thespreading of thel mixture in a thin film on a plate will permit,

the liquid oil to drain away from the bubbles and the water vapor toescape.

Usually on viscous lubricants such as bright stock, a temperature of 150to 200o F. and a vacuum of 27 to 28 inches ona mercury gauge arerequired. I do not limit myself to the exact vacuum and temperature tobe used in this process and apparatus, as this must be determined foreach specic oil to be dehydrated.

'The invention possesses other advantageous features, some of which,with the foregoing, will be set forth at length in the followingdescription, where I shall outline that form of the apparatus which Ihave selected for illustration in the drawing accompanying and formingpart of the present specification, In

mediate pipes 8 storage tank, 2 is a drawoif pipeconnectedl with thesuction side of a pump- 3. Thedischarge from the pump l4 is connected toa heat exchanger 5. A line from the discharge end of the heat exchanger-connects into a perforated pipe 14 positioned in the` vacuum tower 7.rlhe lines 6 are connectedby'interto the semi-circular perforated pipes14 shown diagrammatically by a dotted line in the drawing. Y

At 9is shown a plurality of plates orbafle Y conesover which the oilsprayed from the perforated pipes 14 flows in its passage downwardly'through the tower. l0 and 11 designate two liquid level control deviceswhich are. placed on the vacuum chamber 7. The control 10 communicateswith thepower supu ply to the pump 3, while the control 11 is connectedto Vthe power supply to the pump 20. Thebottom head of the vacuum towerisidesignated'as 12 and the top head as 13. 14,. as suggested, is thevperforated pipe by means ofV which the oil is introducedinto the towerfrom the line 6, and 15 are the oil outlet pipes at the bottomV of thevacuum tower andV 16 is the top vapor withdrawalY A' line whichispreferably welded to the center ff of the removable head 13.

A two-stagey ejector is shown at 17, with thev necessary inlet andvoutlet connections for. maintaining the desired v'acuumf on the system.18 is a vacuum eolualizing*` line which is connected tothe removablehead 18 and to a small intermediate discharge tank 19.V

2O is an automatically controlled pump for removing liquid from thetower and 21 isa cooler through which the discharged oil mayV bencirculated from the pump 20 when the.V

valve 25 is closed and the valve 24 open. 22

is a recirculating line by means of which the oil may be returned to thestorage-tank when the Valve 24 is closed and the valve 25 open;

A? pipe 26 is used for introducing a heating medium to the heatexchanger v5, which medium is discharged from the heat exchanger throughthe pipe 27. In a like mannera cooling'medium is introduced to thecooler 21 through the pipe 28 and discharged through the line' 29.Intermediate connections and necessary bypasses have been omitted fromthe description in the interest of simplicity.

rIhe dehyrator consists of a circular tower 7 which 's closed at thebottom by a bumped Y head l2 and on top by a removable head 13 providingentrance to the interior of the tower. This constitutes the vacuumchamber. At the center of this chamber 7, shell angles are welded to theshell, upon which rests a series of conical plates 9. These conicalplates 9 are-arranged alternately,` one being placed with the apexupward which flows the oil over the outer surface of the cone, and

the second arrangedv with the apex down- Ward, the oilfrom theupper conedraining olf the rim and flowing down the inside of the reverse cone andagaindraining off through a hole provided in the bottom of the reversecone for that purpose, to the next plate which is again turned with. theconeupward, and soV on. down throughthe series. of plates. A

preferred form for theseplates 9 provides a slope to the cone of.15 tothe horizontal, although variations from this are. permissible, the`object being to have such a steepness of slope that thenatural flow ofthe oil film thereon will provide the proper length of time4 to permitthe proper water release to take place. VI have found that various formsof plates as well as chemical Crockery willV have the sameeifect as theconical plates, and I do notlimit; myself to the conical plates, asother means have been` found` to distribute the oil ina multiplicity ofevaporating surfaces. 'Ihese cones arey for the. purpose of causing theoil to flow in a thin film and they are equivalent to added height ofthe tower in that they lengthen theY time that the oil is exposed tothe. influence ofthe vacuum. The

oil inlets 8,.two in number, are placed aboveV theI 4cone plates 9. Theyare welded to the inside shell of the tower and consi-st of a pipe withacompanion flange. To the vinlet' pipes Y 8 arey attached two`semi-circular pipes 14 which are perforated and which are held in placeby Hanges fastened to the companion flange at the shell of the vacuumdrum 7. The-perforations are placed on the bottom of the= semi-circularpipe, so as to spray the oil upward. 'Ihe oil. outlet pipe 15 at thebottom is weldedtangentially to thebottom head` 12 so; asv to--permitcomplete drainage. 'Ihe steam and airoutlet 16v at thetop'of the vacuumchamber is welded in the center of the removable head 13. Baiiles 23 aresuspended from thisremovable head to. collect and return the oil whichis entrained in the escaping steam. Vaccum ismaintained by two stageejectors; 17 with jet condensers be* tween the first; andsecond stagesand onev after the: 'second' stage. This. ejector syst-.em

17 is connected to the steam and air outlet of the'tower. It isnot:desired'to'limitthe invention to this means for obtaining the vacuumand any other suitable means may be used. Y

Two liquid level controllers. 1()Y and 11 are pllaced on thevacuum-chamber 7 just below t e cone. plates 9. Theone level controller11 stops the discharging pump when the oil level falls below this leveland the other controller causes the charging pump to stop `when the oillevel rises above this level. This control prevents the tower frombecoming inundated with the consequent loss of oil through the ejector.These liquid level con trollers are actuated by means of throttledcompressed air as the pumps are at some distance from the controllingball floats. The

vacuum equalizing line 18 is connected to the removable head 13 and tothe small intermediate discharge tank 19 so as to permit the oil to flowout from the bottom of the chamber 7. The remainder of the equipmentconsists` of the usual heat exchangers, coolers, etc.

The following is a description ofv one of the preferred methods ofoperation of the process and is offered in the interest of clari tyingthe disclosure.

The oil to be dehydrated is pumped from storage into the tank 1. Thesteam is then chamber 7. When the controlled lower level of the vacuumchamber 7 is passed, the discharging pump 20 is automatically started bythe lower liquid level controller 11, the valve 24 to the tank car orother iinished oil receptacle closed, and the valve 25 on therecirculating line open. The oil then passes throughline 22 to tank 1.The circulation is `continued until the system is dry and a sample ofthe oil shows dry. If the sample is dry, the water is turned into thecooler 21 on the loading line. The valve to the circulating line isclosed and the valve on the loading line is opened and the loading ofcars is begun. There is a relief valve placed between theloading lineand recirculating line so that when loading from car to car, theoperation of the dehydrator continues uninterrupted by discharging backto tank 1. To dry up the system and get it settled requires aboutone-half hour. After this the only attention required is that the supplyof oil in tankl is not exhausted and continuous dehydration may becarried out.

In actual commercial operation of this process and apparatus describedin the foregoing, 200 barrels per hour was completely dehydrated andloaded into cars and no detectable water was found. During one daysoperation, not running the 24 hours, 3,302 barrels of D stock (heavyviscous lubricant) were loaded into cars.

It has been found in actual practice in the dehydrating of normalmid-continent lubricating stocks that the temperature in the dehydratorruns approximately 190 F. and the temperature of the oil after goingthrough the cooler 21 into the tank cars or into storage is 140 more orless. The normal pressure on the charging pump to the dehydrator is inthe neighborhood of 150 pounds and the pressure on the pump pumping fromthe dehydrator runs from 50 to 55 pounds.

The vacuum maintained on the equipment is an average of 27 to 28% inchesof mercury. In the case of dehydrating certain neutral oils which have amuch lower viscosity than lubricating stocks it will be necessary tocarry the temperature as high as that ordinarily used with highviscosity oils such as bright stocks. Temperatures from 150 to 200 F.would include the normal range necessary for dehydrating mid-continentlubricants.

In actual practice the oil is circulated through the system until theoil in the charging tank has reached a temperature of 130 to 140O F.Vacuum is then imposed on the system and the operation carried out aspreviously described. The temperatures and average vacuum maintainedhave been designated merely for the purpose of giving a typical exampleof the operation of the method constituting the invention, but it is notintended to limit the invention to these particular ranges, as diierenttypes of oils will require varying conditions and the process adaptsitself readily to these necessary variations. The use of hightemperatures obviously reduces the surface tension, producing a thinnerlm and allowing more rapid escape of the moisture. At the same timetemperatures must be properly limited to prevent degrading of the oildue to excessive temperatures.

I claim as my invention:

A process for dehydrating petroleum oils which contain substantially nolow boiling hydrocarbons including the steps of heating the oil to bedehydrated to a temperature not in excess of substantially 200 F.,spraying the oil so heated into a zone maintained at sub-atmosphericpressure, said heating step being performed completely without saidsub-atmospheric pressure Zone, spreading the sprayed oil into aplurality of films within said zone, whereby the vacuum `is adapted torupture the iilm surfaces to liberate the moisture, withdrawing themoisture in the form of vapor separately from and out of contact withthe oil being dehydrated, and separately withdrawing the oil beingdehydrated.

LLOYD L. DAVIS.

